Understanding the voltage inconsistency features in lithium-ion battery module

Abstract

Abusive behaviors can induce voltage inconsistency due to their influence on the basic properties of battery cells. The extraction and identification of voltage inconsistency characteristics serve as vital methods for conducting safety risk assessments and early warnings of batteries. However, the inconsistency features caused by variations in cell's basic properties and various abusive behaviors remain unclear. To address this, a series of battery module cycling tests were conducted to comprehensively analyze inconsistency features and quantify these features using mean normalization (MN) and coefficient of consistency variation methods. Some inconsistency features such as “V-type” and “Λ-type” features, sharp fall feature, and continuous increase of deviation feature, that caused by the variation of initial SOC, capacity, and resistance were captured and quantitatively analyzed. Moreover, the inconsistency features of mechanical deformation, overcharge, over-discharge and low-temperature operation were investigated. “V-type” feature and sharp fall of MN value feature can be found in mechanical deformation, overcharge, and low-temperature operation at 0.5C-rate. For the cell with 6.8 mm indentation depth, the ISC induced continuous increase of low voltage deviation with cycling was also characterized. For low-temperature operation at high C-rates, the “V-type” feature vanished but the sharp fall feature aggravated. These results provide insight into understanding voltage inconsistency features and highlight new directions for safety risk assessment.